DESCRIPTION: The primary objective is to determine minimal sampling frequencies and study duration required to significantly differentiate hormonal secretory patterns between clinically distinct cohorts, via approximate entropy (ApEn), a quantification of sequential irregularity developed by the principal investigator. ApEn has been broadly applied within clinical endocrinology, providing complementary information to pulse detection methods. However, typical protocols employed to generate data sets suitable for 'pulsatility analysis' have required 60-300 samples, rendering such studies largely research (rather than clinical) methods, due primarily to considerable assay expense. In reanalysis of one published hormonal study database, we have realized dramatic reduction in the number of samples required to do discriminatory pulsatility analysis via ApEn. The purpose herein is to augment these finding to determine the breadth of this reductive capability. Such reduction in sampling requirements holds the potential to move pulsatility analysis from a primarily research basis to a clinically applicable protocol, in appropriate diagnostic and therapeutic contexts. Phase I focuses on reanalysis of two classes of tumoral subject data (Cushing's disease and acromegaly), plus younger vs. older male LH and testosterone secretory data. PROPOSED COMMERCIAL APPLICATION: NOT AVAILABLE